Iga Swiatek won her eighth championship of the year in the San Diego Open final on Sunday, defeating Croatia's Donna Vekic 6-3 3-6 6-0.

Swiatek pumped her fist and blew a kiss to the crowd after Vekic double-faulted on match point to cap a third set where the Pole raised her level and tournament qualifier Vekic appeared to finally run out of gas.

"I wanted to go all in," Swiatek said of her approach going into the deciding set of the new WTA 500 event.

"Knowing how well she can serve, I just wanted to be more loosened up on my return games. Not think too much, use my intuition and fight for every ball."

Swiatek got the first break of serve of the match in the opening set when Vekic, who had to complete her rain-interrupted semifinal earlier on Sunday, sent a backhand long for 4-2.

Another backhand error handed Swiatek the first set, prompting Vekic to throw her racket to the court in frustration.

However, Vekic refused to go down without a fight and leveled the match on the strength of her powerful serve and groundstrokes.

In the decider, Swiatek fired a crosscourt winner to break for a 2-0 lead that shifted momentum firmly in her favor.

Swiatek, who rose to world No. 1 in April following Ash Barty's retirement, is now 64-8 on the season. The 21-year-old won the U.S. Open and French Open this year and will be the hot favorite when WTA Finals kick off in Fort Worth on Oct. 31.

Vekic, who underwent knee surgery after last year's Australian Open, can hold her head high after notching wins over Danielle Collins, Aryna Sabalenka and Karolina Pliskova and pushing the world's top player to three sets in the final.

"I'm pretty happy that you're back and hopefully we are going to play many finals," Swiatek said.